Browsing by Subject "Carbides"

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    2D rare-earth metal carbides (MXenes) Mo2NdC2T2 electronic structure and magnetic properties: A DFT + U study
    (AIP, 2022) Yao, Shukai; Anasori, Babak; Strachan, Alejandro; Mechanical and Energy Engineering, Purdue School of Engineering and Technology
    2D rare-earth metal carbides (MXenes) are attractive due to their novel electronic and magnetic properties and their potential as scalable 2D magnets. In this study, we used density functional theory with the Hubbard U correction to characterize the structure, termination, and magnetism in an out-of-plane ordered rare-earth containing M3C2Tx MXene, Mo2NdC2T2 (T = O or OH). We investigated the effect of the U parameter on the stability and magnetism of two possible termination sites: the hollow sites aligned with the inner Nd atoms (Nd-hollow sites) and those aligned with the closest C atoms (C-hollow sites). We found that increasing UMo stabilized the Nd hollow sites, which minimized electrostatic repulsion between C and O atoms. Using UMo = 3.0 eV and UNd = 5.6 eV, obtained via the linear response method, we found that the energetically preferred termination site was C-hollow in Mo2NdC2O2 and Nd-hollow in Mo2NdC2(OH)2. Regardless of termination and the Hubbard U value, we found Mo2NdC2O2 and Mo2NdC2(OH)2 to be magnetic. The C-hollow termination resulted in ferromagnetic states for all Hubbard U tested with no magnetic moment in Mo. In the case of Nd-hollow, Mo became magnetic for UMo ≥ 4 eV. The difference of Mo magnetism in Nd-hollow and C-hollow was explained by crystal field splitting of the Mo d orbital caused by a distorted ligand.
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    Double transition-metal MXenes: Atomistic design of two-dimensional carbides and nitrides
    (Cambridge UP, 2020-10) Hong, Weichen; Wyatt, Brian C.; Nemani, Srinivasa Kartik; Anasori, Babak; Mechanical Engineering and Energy, School of Engineering and Technology
    MXenes are a large family of two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides. The MXene family has expanded since their original discovery in 2011, and has grown larger with the discovery of ordered double transition-metal (DTM) MXenes. These DTM MXenes differ from their counterpart mono-transition-metal (mono-M) MXenes, where two transition metals can occupy the metal sites. Ordered DTM MXenes are comprised of transition metals in either an in-plane or out-of-plane ordered structure. Additionally, some DTM MXenes are in the form of random solid solutions, which are defined by two randomly distributed transition metals throughout the 2D structure. Their different structures and array of transition-metal pairs provide the ability to tune DTM MXenes for specific optical, magnetic, electrochemical, thermoelectric, catalytic, or mechanical behavior. This degree of control over their composition and structure is unique in the field of 2D materials and offers a new avenue for application-driven design of functional nanomaterials. In this article, we review the synthesis, structure, and properties of DTM MXenes and provide an outlook for future research in this field.